Congestive heart failure (CHF), or simply heart failure, is a condition in which a damaged heart muscle is unable to pump sufficient blood to meet the body's demands, first in the early stages, only during exercise, but later in advanced stages, even during rest. It is an important and common disease having numerous etiologies and afflicting millions of Americans with up to 400,000 new cases yearly. It is the most common diagnosis in hospital patients over 65.
It is well known that CHF patients, although usually stable, can nevertheless decompensate from time-to-time, even to the extent that their life may be threatened by, e.g., hypotension or pulmonary edema. Decompensation typically occurs because proper functioning of the cardiovascular system requires that cardiovascular parameters be in balance, and although this balance is routinely maintained in health by normal physiological controls, the normal controls can become inadequate in CHF. Medical treatment is then necessary to restore the cardiovascular system to balance and to maintain it in balance. But balance achieved by medical treatment is often not robust and can be easily disturbed. CHF patients have insufficient cardiovascular reserve with which to compensate for unexpected or unpredicted variation in their medical treatments. A CHF patient who is controlled one week, may decompensate the following week.
Such variations in medical treatment can be all too common events. According to current practice, CHF treatment generally includes encouraging advantageous nutritional and lifestyle habits along with prescribing cardiovascular active drugs when necessary. It is well known that patient behavior, such as nutrition and lifestyle, is notoriously unpredictable and resistant to change. For example, although a patient may be well aware that, because fluid overload readily occurs in CHF, it is advisable to limit salt and water intake, that patient may from time to time ingest excessive salt and decompensate. Also, although the patient is aware that lower body weight and cessation of smoking are highly desirable, the patient may nevertheless from time-to-time overeat and smoke. Both these behaviors, if continued over time, can lead to decompensation.
Less well known, perhaps, is that maintaining a proper dose of cardiovascular active drugs can be equally difficult. Drugs, which at one dose usefully treat CHF, can, at another dose, exacerbate CHF. For example, diuretics can cause potassium deficiency which leads to abnormal cardiac rhythms and decreased cardiac output. Digitalis, an important drug in CHF, has a narrow therapeutic range. If too much digitalis accumulates in the blood, it can become toxic instead of therapeutic. A forgetful patient skipping a dose, doubling a dose, or otherwise taking improper doses can decompensate.
It is apparent, therefore, that automatic methods and systems that can monitor CHF patients for signs of decompensation can be useful for managing their treatments and maintaining their health. It is further apparent that such monitoring methods and systems can be even more useful if patient monitoring is possible without expert assistance and while patients perform their normal daily activities. Such cardiovascular monitoring systems capable of useful monitoring of CHF patient during their normal daily activities are not believed to be known in the prior art.
Citation or identification of any reference in this section or in any section of this application shall not be construed as an admission that such reference is available as prior art to the present invention.